The case I'm using is only 70mm tall, so you should be good. I keep reading about how much heat the line stage makes, so I have a vented top cover to allow air flow and heat dissipation. I'm also using the silicone heat transfer paste between the MOSFETS and the heat sink, just a dab.

Here is my completed power supply for BZLS. I added a pair of 110vac outlets which are switched by the front panel switch (left over from my ACA kits), One outlet is for the power strip for the ACA power supply's. The other is for a second power strip for my Wadia 170, Music Hall 25.3 DAC, Marantz 110 tuner and a Denon CD player/transport.

No, they are 3 pin microphone connectors, identical to Radio Shack 4 pin microphone connectors. They use a 5/8" hole in the rear panel, and then have a slot in the plastic which aligns with a pin in the chassis connector so they only fit together one way.

You're way ahead of me! Just ordered the Galaxy 2U chassis from the store and am waiting for my XLR/RCA jacks and my pots to arrive. But as I lay out the transformers and PCBs on my workbench and try to visualize it, I realize I have no idea how to wire anything other than the power supply, for which N.P.'s directions are very clear. But as far as wires from the input jacks to, what, selector switch? Not a clue. If anyone can point me the right direction I'd appreciate it.

Is there a good preamp wiring article or graphic anyplace. I've searched a number of BOSOZ posts but never see anything as basic as what I'm going to need.

The inputs (XLR and/or RCA's) go directly to the selector switch inputs. If you are going to have an input with BOTH XLR and RCA in parallel, then you wire the XLR to the selector switch and the RCA's are wired off the XLR connector. This is described on page 6 of the article. You will have to decide with XLR pin 2 or 3 is for the left or right channel. Wire them one at a time in regards to left and right.
XLR pin 1 goes to RCA grounds.
XLR pin 2 goes to "live" or the center pin of the positive RCA
XLR pin 3 goes to "live" or the center pin of the negative RCA
The selector switch outputs (there will be 4: L+, L-, R+, R-) will have R18 & R19 (times 2, 220 ohm) which will go to the 10K pot. with the variable or center lead.
The 10K pot then goes to the PC board.
The XLR output wiring will be the same pin assignments.
I have 24 awg wire in 6 colors which I will twist 3 together so I don't get confused wiring from the inputs to the selector switch.

Where I struggle is with which channel (left or right) is positive and which is negative in regards to the RCA's?
This is where I'm hoping someone smarter than me will chime in.
Does this help?

Yeah, I saw the explanation, and I don’t get it either. On our ACAs, the RCA jacks were just positive pin/negative collar. One was left channel and one was right channel. The whole balanced thing is confusing but I want to use it. Thanks for trying.

Hey, I have a Music Hall 25.3 DAC , too. I think I prefer it in balanced mode into the ACAs — opposite of what I assumed I’d like. I replaced the stock tube with a JJ chasing some more warmth, but didn’t really hear a change.

I looked at the build guide for the ACA v1.6:
XLR pin 2 goes to Right RCA center pin
XLR pin 3 goes to Left RCA center pin
XLR pin 1 is ground
The RCA collar goes to ground for both channels, so "postive" is Red and Right, "negative" is Left and White.

So when wiring XLR and RCA in parallel, the Right channel XLR will have pin 2 to the Right RCA. Left channel XLR will have pin 3 to the Left RCA.